The present invention relates to a multi-blade inner hole saw for the sawing of crystal rods into thin wafers and separating operations carried out by means of this saw.
For the manufacture of electronic components or solar cells, it is often necessary to provide the semiconductor or oxidic material used, that is, silicon, germanium, gallium arsenide, indium phosphide, sapphire or gallium-gadolinium garnet, in the form of thin wafers of, typically, 0.1 to 1 mm thickness. These thin wafers are obtained as a rule by sawing the starting material which is available in the form of crystal rods or blocks. In most cases, this sawing operation is carried out with the aid of inner hole saws.
In the case of known inner hole saws, the saw blade is braced at the outer edge in a frame. This is held by a cup-like widening frame support, which is attached at one end of a drive cylinder borne usually by means of a ball, air or hydrodynamic bearing and set in rotation via a drive unit. This one-sided, top-heavy arrangement causes an uneven stressing of the bearings, which reduces the wear resistance and service life, and a slight inclination of the saw blade, which has unfavorable effects on the cutting profile and the cutting accuracy. This effect is all the more marked the more top-heavy the arrangement is, so that inner hole saws with several saw blades, for example, according to German Offenlegungsschrift No. 3,216,200 the entire disclosure of which is incorporated herein by reference, are naturally more affected than those with only one saw blade. The higher cutting capacity is therefore always achieved with multi-blade arrangements at the expense of cutting precision and service life, which is unsatisfactory in view of constantly increasing accuracy requirements.